Rheostatic regulator



Deal, 1941- J. F. KOVALSKY 2,264,935

RHEOSTATIC REGULATOR Filed Jan. 13, 1938 mm 1 INVENTOR AMA- Jase "072 F/r UOZSQZA Patented Dec. 2, 1941 anaos'ra'nc aacunaroa Jooepln F.KovaIaky,TartleCrcek,Pa.,anignor u Westinghouse Electric 1; Manufacturing Ompany,EatPltisbargh,Pa.,acorporation of Pennsylvania Application 13, 1938, Serial No. 184,838

Claims.

My invention relates to regulator systems and particularly to control m for governing a rheostatic type regulator.

In rheostatic type fl ators, it is customary to provide a rheostat operating motor controlled by reversing switches or secondary relays, for controlling the operation of the motor in the 0. or the other direction, and that are in turn controlled by a primary relay that is actuated in accordance with the quantity to be regulated, such as the voltage of a generator. It is also customary to provide condenser timing circuits in parallel circuit relation to each of the operating windings of the secondary relays, which are charged during the energization of the relay operating winding, this charge being employed as a source of energy to maintain the winding of the switch energized for a short time after the energizing circuit is interrupted by the primary relay. This insures a time delay opening characteristic of the reversing switches or secondary relays, so as to insure that when the relay has operated to a motor energizing position, the motor will operate the rheostat sufficiently to advance the rheostat arm'at least from one rheostat button to the next adjacent button so as to insure one step of change in the rheostat resistance.

In the usual manner of connecting condense timing circuits, the relatively large condenser charging current which temporarily flows upon engagement of the primary relay contact members burns the contact members in a relatively short time. If a high resistance is added in series with the condenser to limit the charging current,

the condenser will not receive a full charge in the 35 short time that the primary relay contacts are likely to be maintained in engagement.

It will be appreciated that the contact members of a relay, such as a contact-making voltmeter, do not close positively with appreciable 40 pressure as in the case of a circuit controlling contactor, but move into engagement slowly and touch initially with very light contact pressure. The initial contact resistance is, therefore, high so that most of the voltage drop in the circuit is across the contact members and a relatively small portion thereof is impressed across the winding of the secondary relay. The secondary relay coil may not, therefore, be energized suiiiciently to cause it to immediately operate to a circuit closing positionand the primary relay contacts tend to fry or are until suflicient contact pressure is made to cause the secondary relay to operate.

The above-described circuit is eifective when 5 and comprises a core 21 in the form of a substanchanges in voltage are sudden and suflicient in amount to close the primary relay contact members with considerable pressure and maintain them closed for an appreciable time, but on circuits where the contact members may engage momentarily and with only very light pressure, the contact members will burn appreciably.

It is an object of my invention to provide a regulator of the above-indicated character in which means is provided for preventing burning of the primary relay contact members due to charging current of the condenser timing circuit associated with the windings of the secondary relays.

Other objects. and advantages .of my invention will be apparent from the following description of certain preferred embodiments thereof, reference being had to the accompanying drawing, in which:

Figure l is a diagrammatic view of circuits and apparatus arranged in accordance with the conventional or above-described circuit;

Fig. 2 is a diagrammatic view of circuits and apparatus illustrating one preferred embodiment of the invention; and

Fig. 3 is a diagrammatic view of circuits and apparatus illustrating a second preferred form of the invention.

Referring to Fig. 1, a direct-current generator is illustrated having an armature winding I for supplying energy to an electric circuit indicated by conductors 2 and 3, and a field winding 4 that is connected to be supplied with energy from an exciter generator having an armature 5 and a field winding 6 that is connected in shunt relation thereto, through an adjustable rheostat The armature 5 of the exciter generator is connected to the field winding 4 by conductors 8 and 8 through a rheostat l2 having a'resistor I3, tap points of which are connected to a plurality of contact buttons II that are engaged by a movable arm l5 operated through gearing mechanism It by a rheostat motor ll. The motor I! comprises an armature winding l8 and differentially related field windings l9 and 22 that are adapted to be connected to a source of energy, such as the battery 23, upon closure of either of two reversing switches 24 and 25 that are controlled by operation of a primary relay 26.

The primary relay 2! may be of any suitable type, and is here diagrammatically illustrated as of the construction disclosed and claimed in application of Clinton R. Hanna for Voltage regulators, Serial No. 118,554, filed December 31, 1936,

tially closed loop provided with an air gap in which an armature 26 is adapted to move. The armature is carried by a lever 26 pivoted on a pin 32 and carrying a movable contact 33 that is adapted to engage fixed contact members 34 and 35. A spring 36 is provided for normally biasing the lever 29 away irom the core in opposition to the pull of the core as magnetized by a winding 31 that is connected by conductors 36 and 36 to conductors 2 and 3, respectively, to be energized in accordance with the voltage of the generator armature I.

It the voltage of the generator armature I drops below its desired value, the pull oi the core 21 upon the armature 26 will decrease and the spring 36 will cause the contact member 33 to engage the contact member 34 and'close a circuit from a battery 42 through conductor 43, contact members 33 and 34, conductor 44, the winding. 45 of the relay 24 and conductor 46 to the opposite terminal of the battery 42. The closing of the above traced circuit energizes the reversing switch 24 moving it upwardly to its circuit closing position in which the contact member 41 engages the contact member 48 to close a circuit through the field winding 19 and the armature winding I6 of the rheostat motor 11 to operate the arm IS in a counter-clockwise direction to decrease the value of the resistance l3 in circuit with the generator field winding 4 and thereby increase the energization thereof and the voltage of the armature winding I As the voltage builds up across the winding 45 of the secondary relay 24, a corresponding voltage builds up across the condenser 46 that is connected in series with a resistor 52 in shunt relation with the winding 45 to provide a timing circuit for maintaining the winding 45 energized for a short interval of time after separation of the primary relay contact members 33 and 34 to inwill remain closed a suilicient length of time to permit the rheostat arm l to be moved from one rheostat button 14 to the next adjacent button to thereby efi ect a change in the resistance i 3 corresponding to one rheostat step upon, a momentary engagement of the primary relay contact members. As the generator voltage builds up, the contact member 33 is moved out of engagement with the contact member 34 to interrupt the operation of the motor l1.

Should the voltage between conductors 2 and 3 increase above the desired value, the pull of the core 21 on the armature 26 against the pull of the spring 36 causes engagement of the contact members 33 and 35 to close a circuit from the battery 42 through conductor 43, contact members 33 and 35, conductor 54 and the winding 55 of the reversing switch to the opposite terminal of the battery 42 to operate the reversing switch 25 to a circuit closing position causing the contact member 56 to engage'the contact members 51 and close a circuit from the battery 23 through contact members 56 and 51, field winding 22 and armature winding 16 to operate the motor l1 and move the rheostat arm I 5 in a clockwise direction to increase'the portion of the resistor l3 that is in series with the generator field winding 4 to thereby decrease the generator voltage.

A timing circuit consisting of a condenser 43 in series circuit relation with a resistor 52 is connected in shunt relation to the winding 55 of the secondary relay 25 which corresponds in structure and function to that provided and associated V with the secondary relay 24.

sure that the reversing switch 24, when closed, I

iii

It will be appreciated that as the movable contact member 33 floats into engagement with either oi thecontact members 34 or 35 at light pressure, a comparatively large charging current flows to the associated condenser 43 of the timing circuit.

Referring to Fig. mm which a portion only of the mechanism is illustrated, the remaining or unillustrated portions corresponds to that illustrated in Fig. l. A timing circuit associated with each oi! the secondary relays 24 and 25 is provided and comprises a condenser 62 connected in series circuit relation with a resistor 63, these series connected elements being adapted to be connected in shunt relation to the relay winding 45 through a contact member 64 that bridges contact members 65 upon operation of the switch 24 to its circuit closing position. A resistor 66 is also provided in shunt relation to the winding 45 that is 01' larger resistance value than the resistor 53. The inductive energy stored in the winding 45 is discharged through the resistor 66 upon separation of the primary relay contact members 33 and 34 thus reducing the arcing at the contact members. The value of the resistor 66 is so proportioned that the desired current flow from the condenser 62 through the relay winding 45 maintains the relay .closed for the desired length of time. The general operation of the system in Fig. 2 is the same as that in Fig. 1 so far as the rheostat and its motor are concerned. However, the condenser timing circuit is not charged immediately upon engagement of the primary relay contact members, but only after the flow of current through the primary relay contact members suilicient to operate the secondary relay 24 to its circuit closing position has caused engagement of the auxiliary contact members 64 with the contact members 65. The condenser time delay circuit associated with the secondary relay 25 is identical with that-described as associated with relay 24, and is illustrated as consisting of correspondingly numbered condenser 62 and resistors 63 and 66, the resistor 66 being connected in shunt relation with the relay winding and the condenser circuit being connected in shunt relation thereto upon engagement of the auxiliary switch contact member 61 with the contact members 68 as the switch 25 is operated to, its motor circuit closing position.

Fig. 3 illustrates a second modification of the invention in which a condenser 12 is connected in series circuit relation with a resistor 13 in shunt relation with the winding 45 of the reversing switch 24 through auxiliary switch contact members 64 and 65. In this embodiment of the invention, no resistor is provided corresponding to 66 shown in Fig. 2, but a condenser 14 is provided across the terminals of the auxiliary switch contact members,'the condenser 14 having relatively small capacity as compared to condenser 12. For example, condenser 12 may have a capacity of 40 microfarads and the condenser A 14 a capacity of l microiarad. Condensers 12 the capacitance in parallel with the winding 45 is determined by the product of the capacities of the two series connected condensers divided by their sum, or 1X40 divided by 1+40 equals .98 microfarad. This value is small enough to prevent arcing at the primary relay contact members and is also large enough to prevent any arcing at the contact members caused by an inductive kick from the winding 45 which will be discharged through the series connected condensers I4 and 12 and resistor 13. When the interlock switch 64 closes, the full capacity of the condenser '12, namely -10 microfarads, is connected in shunt relation to the winding 45, the charge upon which provides the time delay operating characteristics of the switch 24 in opening.

Many modifications will appear to those skilled in the art without departing from the spirit of my invention, and I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention? 1. In a regulator system employing an electric motor and means actuated thereby for varying a quantity to be regulated, in combination, an-

electrically operated switch having an operating winding and adapted to be actuated to its circuit closing position when energized, a resistor connected in parallel circuit relation to the switch operating winding, a condenser, and means operated upon operation of said switch to a circuit closing position for supplying charging current to said condenser.

2. In a regulator system employing an electrical circuit and motor operated means for controlling an electrical characteristic of said circuit, in combination, a pair of switches having operating windings adapted to operate the switches to their circuit closing positions when energized, a contact making relay for controlling said switches, a. timing circuit for each switch comprising a condenser and resistor connected in series relation with each other and in shunt relation to the operating winding oi the associated switch, a resistor connected in parallel circuit relation to the switch operating winding of larger resistance value than the above-named resistor, and means controlled by operation of said switch to a circuit closing position for charging said condenser,

3, In equipment of the class described, an electrically operated switch having an operating winding and adapted to be actuated to its cir cuit closing position when the operating winding is energized, a timing circuit for the switch including a resistor connected in parallel circuit relation to the operating winding, a condenser, and means efiective only upon operation of the switch after energization of the operating winding for supplying charging current to said condenser.

4. In equipment of the class described, an electrically operated switch having an operating winding, a timing circuit for the switch including a condenser and resistor connected in series relation with each other, a resistor connected in parallel circuit relation to the switch operating winding, and means controlled by operation of the switch upon energization of the operating winding for connecting the timing circuit in parallel relation to the operating winding.

5. In equipment of the class described, an electrically operated switch having an operating winding, a timing circuit for the switch including a condenser and a resistor connected in series circuit relation with each other and adapted to be connected in shunt relation to the operating winding, a' resistor connected in parallel circuit relation to the switch operating winding of larger resistance value than the above-named resistor, and means including an auxiliary contact controlled by operation of the switch upon energize.- tion of the operating winding for connecting the timing circuit in parallel relation to the operating winding.

JOSEPH F. KOVALSKY. 

